05 February 2009

Sex change for survival

As with orchids and some trees, some corals may survive bad times by changing sex."One of the evolutionary strategies that some corals use to survive seems to be their ability to change from female to male," says Prof Yossi Loya. "As males, they can pass through the bad years, then, when circumstances become more favorable, change back to overt females. Being a female takes more energy. And having the ability to change gender periodically enables a species to maximize its reproductive effort."Females turn into males when times get tough... on the sea floor, that isJudy Siegel Jerusalem Post 4 Feb 09;

Without intending to provide ammunition for the current argument over whether a woman would be as competent as a man in the prime minister's hot seat, Tel Aviv University scientists have found that when times get tough, nature sends in the boys - at least when it comes to an important species of coral.

TAU zoology Prof. Yossi Loya is the first in the world to discover that Japanese sea corals engage in "sex switching" under periods of stress, especially when threatened by global warming, The Jerusalem Post has learned. The fragile, flower-like sea animals are essential to all life in the ocean.

In times of stress such as extreme hot spells, the female mushroom coral (known as a fungiid coral) switches its sex so that most of the population becomes male.

The advantage of doing so, says the world-renowned coral reef researcher, is that male corals can more readily cope with stress when resources are limited.

"We believe, as with orchids and some trees, sex change in corals increases their overall fitness, reinforcing the important role of reproductive plasticity in determining their evolutionary success," says Loya, whose findings have just appeared in the Proceedings of the Royal Society B.

"One of the evolutionary strategies that some corals use to survive seems to be their ability to change from female to male," adds Loya. "As males, they can pass through the bad years, then, when circumstances become more favorable, change back to overt females. Being a female takes more energy. And having the ability to change gender periodically enables a species to maximize its reproductive effort."

Corals, though a part of the animal kingdom, can act like plants. Both are sedentary life forms, unable to move when times get tough. In stressful environmental conditions, male corals can "ride out the storm," he notes. "In the evolutionary sense, males are less expensive to maintain. They are cheaper in terms of their gonads and the energy needed to maintain their bodies," he says. He adds that this theory probably doesn't apply to humans, even those who have opted for a sex change.

While admired for their beauty by divers, coral reefs provide an essential habitat for thousands of species of underwater creatures. Without the reefs, much of the underwater wildlife in reef habitats would perish. And for millions of people in the tropical regions, coral reef sea life is a major source of daily protein.

Coral reef destruction, however, is expected to continue as an effect of global warming. About one-quarter of coral reefs around the world have already been lost. The TAU zoologist's finding may give new insight to scientists into developing coral breeding strategies for the time when the massive climate changes predicted by scientists set in.

"This knowledge can help coral breeders. Fungiid corals are a hardy coral variety that can be grown in captivity. Once you know its mode of reproduction, you can grow hundreds of thousands of them," says Loya, currently involved in coral rehabilitation projects in the Red Sea. He has been studying coral reefs for more than 35 years and won the prestigious Darwin Medal, awarded every four years by the International Society for Coral Reefs, for a lifetime contribution to the study of coral reefs.

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